Re: brcmfmac disconnects when iwd scans

On 5/3/2025 1:43 AM, KeithG wrote:
> On Fri, May 2, 2025 at 11:38 AM Arend Van Spriel
> <[email protected]> wrote:
>>
>> On May 2, 2025 6:10:35 PM KeithG <[email protected]> wrote:
>>
>>> On Fri, May 2, 2025 at 9:45 AM Denis Kenzior <[email protected]> wrote:
>>>>
>>>> Hi Keith,
>>>>
>>>>> I am building iwd from git with those 3 patches and every time it
>>>>> scans, it disconnects the AP.
>>>>> When I use wpa_supplicant, it does not disconnect regardless of using:
>>>>> iw wlan0 scan passive
>>>>> or
>>>>> iw wlan0 scan
>>>>>
>>>>> it is only with iwd that it disconnects and only with iwctl. If I run
>>>>> 'iw wlan0 scan passive' or
>>>>> 'iw wlan0 scan' when iwd is running and wpa_aupplicant is removed, It
>>>>> seems to be OK.
>>>>> My laptop shows a disconnect, sometimes, but when I check the wlan0 on
>>>>> the laptop
>>>>> it is still connected to the ap running on the RPi. I think it looses
>>>>> the connection for a
>>>>> second but reconnects. If I run the 'iwctl station wlan0 scan' it will
>>>>> disconnect and not reconnect.
>>>>> When it does, the ap0 gets to a strange state as it takes a number of
>>>>> attempts to get it to
>>>>> reconnect and sometimes it requires a tear down and restart of ap0
>>>>> before I can reconnect
>>>>>
>>>>> This is an iwmon log of my RPi.
>>>>> https://drive.google.com/file/d/1WNZz0dOip0XZZVIOs7RGcYIeLY2W4bXC/view?usp=sharing
>>>>> I had connected to it from my laptop. I then ran:
>>>>>
>>>>> # iw wlan0 scan
>>>>> # iw wlan0 scan passive
>>>>> # iwctl station wlan0 scan
>>>>>
>>>>> after I ran the last command, the Pi's ap0 disconnected from my laptop.
>>>>
>>>> I do indeed see the local AP interface generating 'Del Station' events, which
>>>> means the local client was disconnected.  The funny part is that iwd ends up
>>>> scanning a subset of the frequencies triggered via 'iw', it just does it in two
>>>> sets.
>>>>
>>>> Here's what I see iw doing:
>>>>
>>>> < Request: Trigger Scan (0x21) len 16 [ack]                           22.190542
>>>> Interface Index: 3 (0x00000003)
>>>> Scan Flags: Mask: 0x00004000 len 4
>>>>      Colocated6G
>>>>> Event: Trigger Scan (0x21) len 364                                  22.194336
>>>> Wiphy: 0 (0x00000000)
>>>> Interface Index: 3 (0x00000003)
>>>> Wireless Device: 1 (0x0000000000000001)
>>>> Scan SSIDs: len 0
>>>> Scan Frequencies: len 320
>>>> 0: 2412 (0x0000096c)
>>>> 1: 2417 (0x00000971)
>>>> 2: 2422 (0x00000976)
>>>> 3: 2427 (0x0000097b)
>>>> 4: 2432 (0x00000980)
>>>> 5: 2437 (0x00000985)
>>>> 6: 2442 (0x0000098a)
>>>> 7: 2447 (0x0000098f)
>>>> 8: 2452 (0x00000994)
>>>> 9: 2457 (0x00000999)
>>>> 10: 2462 (0x0000099e)
>>>> 11: 5170 (0x00001432)
>>>> 12: 5180 (0x0000143c)
>>>> 13: 5190 (0x00001446)
>>>> 14: 5200 (0x00001450)
>>>> 15: 5210 (0x0000145a)
>>>> 16: 5220 (0x00001464)
>>>> 17: 5230 (0x0000146e)
>>>> 18: 5240 (0x00001478)
>>>> 19: 5260 (0x0000148c)
>>>> 20: 5280 (0x000014a0)
>>>> 21: 5300 (0x000014b4)
>>>> 22: 5320 (0x000014c8)
>>>> 23: 5500 (0x0000157c)
>>>> 24: 5520 (0x00001590)
>>>> 25: 5540 (0x000015a4)
>>>> 26: 5560 (0x000015b8)
>>>> 27: 5580 (0x000015cc)
>>>> 28: 5600 (0x000015e0)
>>>> 29: 5620 (0x000015f4)
>>>> 30: 5640 (0x00001608)
>>>> 31: 5660 (0x0000161c)
>>>> 32: 5680 (0x00001630)
>>>> 33: 5700 (0x00001644)
>>>> 34: 5720 (0x00001658)
>>>> 35: 5745 (0x00001671)
>>>> 36: 5765 (0x00001685)
>>>> 37: 5785 (0x00001699)
>>>> 38: 5805 (0x000016ad)
>>>> 39: 5825 (0x000016c1)
>>>> Scan Flags: Mask: 0x00004000 len 4
>>>>      Colocated6G
>>>>
>>>> While iwd does:
>>>> < Request: Trigger Scan (0x21) len 64 [ack]                           31.619536
>>>> Wireless Device: 1 (0x0000000000000001)
>>>> Information Elements: len 12
>>>> Extended Capabilities: len 10
>>>>      Capability: bit 19: BSS transition
>>>>      00 00 08 00 00 00 00 00 00 01                    ..........
>>>> Scan Frequencies: len 24
>>>> 0: 2412 (0x0000096c)
>>>> 1: 2437 (0x00000985)
>>>> 2: 2462 (0x0000099e)
>>>> Scan Flags: Mask: 0x00004002 len 4
>>>>      Flush
>>>>      Colocated6G
>>>>
>>>> then
>>>> < Request: Trigger Scan (0x21) len 248 [ack]                          32.040780
>>>> Wireless Device: 1 (0x0000000000000001)
>>>> Information Elements: len 12
>>>> Extended Capabilities: len 10
>>>>      Capability: bit 19: BSS transition
>>>>      00 00 08 00 00 00 00 00 00 01                    ..........
>>>> Scan Frequencies: len 208
>>>> 0: 5180 (0x0000143c)
>>>> 1: 5200 (0x00001450)
>>>> 2: 5210 (0x0000145a)
>>>> 3: 5220 (0x00001464)
>>>> 4: 5240 (0x00001478)
>>>> 5: 5260 (0x0000148c)
>>>> 6: 5280 (0x000014a0)
>>>> 7: 5300 (0x000014b4)
>>>> 8: 5320 (0x000014c8)
>>>> 9: 5500 (0x0000157c)
>>>> 10: 5520 (0x00001590)
>>>> 11: 5540 (0x000015a4)
>>>> 12: 5560 (0x000015b8)
>>>> 13: 5580 (0x000015cc)
>>>> 14: 5600 (0x000015e0)
>>>> 15: 5620 (0x000015f4)
>>>> 16: 5640 (0x00001608)
>>>> 17: 5660 (0x0000161c)
>>>> 18: 5680 (0x00001630)
>>>> 19: 5700 (0x00001644)
>>>> 20: 5720 (0x00001658)
>>>> 21: 5745 (0x00001671)
>>>> 22: 5765 (0x00001685)
>>>> 23: 5785 (0x00001699)
>>>> 24: 5805 (0x000016ad)
>>>> 25: 5825 (0x000016c1)
>>>> Scan Flags: Mask: 0x00004002 len 4
>>>>      Flush
>>>>      Colocated6G
>>>>
>>>> And about 1.5 seconds later the Del Station event comes in.
>>>>> Event: Del Station (0x14) len 32                                    33.560662
>>>> Interface Index: 7 (0x00000007)
>>>> MAC Address 50:84:92:A6:7A:7A
>>>> Generation: 0 (0x00000000)
>>>> Station Info: len 0
>>>>
>>>> Not really sure what could be causing this.  Maybe this is a question for
>>>> Arend?
>>>>
>>>> Regards,
>>>> -Denis
>>>
>>> Denis,
>>>
>>> Thanks for going through this. I am still trying to get more pertinent
>>> information as to what may cause these disconnects. If there is
>>> anything I can test or more info I can provide, let me know. As it is,
>>> I am trying to set up hostapd/wpa_supplicant to see if it is any more
>>> stable.
>>
>> So is this thread in any way related to the thread with subject "Cannot
>> maintain an ap with brcmfmac"? I responded to that on April 21, but never
>> saw any follow-up on that. It's kinda hard to debug by email especially
>> when new threads are started in parallel. More than willing to help but a
>> bit lost in the woods here.
>>
>> Regards,
>> Arend
>>
> Arend,
> 
> Sorry about that, Yes it is the same. I stopped responding to that
> thread as it seemed to me to be be an IWD issue and not a
> wpa_supplicant/hostapd/firmware/driver issue that I was running into.
> It still may be, but I thought I'd investigate iwd first. I composed a
> whole response, but then noticed that it seemed more stable with
> wpa_supplicant than iwd and did not want to exercise everyone (you).

No problem. Glad we have it clarified. With user-space and kernel driver 
interacting it is good to keep both sides in the loop and stick with a 
single email thread.

> my next steps are to reconfigure everything with just
> hostapd/wpa_supplicant and see if it is any more stable. If so, then
> look to see if I can characterize how it behaves differently with iwd
> than wpa_supplicant.

You could try without encryption if that is possible to see if that 
makes a difference. Also would help if you enabled CONFIG_BRCMDBG for 
the brcmfmac driver so you can enble additional debug prints by passing 
the 'debug' module parameter. CONN, EVENT, and FIL debug levels are good 
to have and maybe SCAN => debug=0xd400.

> What we want is to be able to use the single WiFi chip with 2
> interfaces, one as the default alan0 and one as ap0 . Have it scan
> automatically on wlan0 while ap0 is up and advertising if not
> connected. If the scan shows a 'known network', tear down off the ap0,
> stop hostapd and initiate a connection to the SSID on the wlan0. We
> create the ap0 via these commands:

Okay. That sounds a bit peculiar. So what is the idea here. When it is 
not connected and running ap0 clients can connect to it and then what? 
Is the use-case here that those client can setup 'known networks'? 
Anyways, you have your reasons and leave it with that.

> iw dev wlan0 interface add ap0 type __ap
> ip link set dev ap0 address '$some_MAC'
> ip link set dev ap0 up

Would it be sufficient to only create the ap0 interface and leave the 
rest to hostapd/iwd. I am pretty sure hostapd does take care of those steps.

Regards,
Arend